(60) باب صِيَامِ أَيَّامِ الْبِيضِ ثَلاَثَ عَشْرَةَ وَأَرْبَعَ عَشْرَةَ وَخَمْسَ عَشْرَةَ
Narrated Abu Huraira:
My friend (the Prophet (ﷺ) ) advised me to observe three things: (1) to fast three days a month; (2) to pray two rak`at of Duha prayer (forenoon prayer); and (3) to pray witr before sleeping.
Reference: Sahih al-Bukhari 1981
In-book reference: Book 30, Hadith 88
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 31, Hadith 202